This invention relates to catheters of preformed shape for insertion into the human body for a variety of purposes, and to the manufacture of such catheters, the sterilization and storage of them until ready for use, and the reclamation, reworking and restorage of them for additional use.
Reuse of catheters of preformed shape before the present invention was difficult, and in many cases impossible, making it necessary to discard such a catheter after a single use. This was occasioned by the fact that the Freon or other gases used to sterilize the catheters tended to soften them and tended to cause them to lose their preformed shape. Also, many of the best materials for manufacture of these catheters become free form at around 100.degree. C.; and in cleaning and sterilizing the catheters for reuse, any time this temperature was reached or approached, the preformed shape of the catheter tended to be lost.
Before the present invention, in order to preform the catheter to the desired preformed shape so that it could be reused, it was necessary to insert a bendable, non-resilient wire through the center of the catheter, and to bend the wire and the catheter into what the technician or doctor considered the best preformed shape before sterilization thereof. This wire-catheter combination was then put inside of a gas permeable plastic bag which was sealed, and then put into a gas sterilizer or gas clave unit. In the sterilizer, the pressure was increased at least slightly above atmospheric, and the temperature raised to about the free form temperature of .[.100.degree. C..]. .Iadd.115.degree. F. .Iaddend.The ethylene oxide or Freon, or other suitable sterilizing gas, was introduced into the sterilizer and allowed to permeate throughout the plastic bag, and through the side walls of the catheter. See U.S. Pat. No. 3,612,038, granted Oct. 12, 1971 to J. C. Halligan.
Unfortunately, there was no effective way to determine the action of the sterilizing gas medium on bacteria which would be lodged between the side wall of the catheter and the stiffening wire. Thus no positive assurances could be given that the sterilization was complete. Further, even though sterile, it was objectionable to introduce a wire into the catheter and then take it out just before the catheter was introduced into the body, because of the possibility that some deleterious material had adhered to the stiffening wire and would be scraped from it and thus would remain inside of the catheter.
In order to manufacture and to initially preform catheters before the present invention, solid metal plates were laboriously grooved out to form exact representations of both sides of the negative image of the catheters, and the catheters were confined in these aligned, facing, hemispherical grooves while they were heated to be preformed. This procedure was, of course, costly and unwieldy, and basically only usable at the point of manufacture of the catheter. Even so, these devices were somewhat effective. They were completely ineffective, however, in the manufacture of shapes which did not lie in a single plane. For example, production of a "pigtail" catheter, where the leading edge is shaped like a portion of a corkscrew, were impossible using the aforesaid method. Here only the stiffened insert wire method could be used, with its questionable sterilization practice and with its inaccuracy in forming and holding the desired shapes.
After catheters were properly formed by the old methods, it was extremely difficult to safely maintain them in a sterilized condition, to store them indefinitely and effectively until needed, and to transport them from the place of manufacture to the place of use. If, in storage or transportation, the catheters were bent out of the desired final preformed shape, any time they were accidentally subjected to heat .[.over 100.degree. C..]. .Iadd.about 115.degree. F., .Iaddend.they would become free form, and when cooled again, would have the preset form of the shape in which they were stored rather than the shape in which they were formed. Even when catheters were cushioned between gauze layers and the like, and stored in boxes each large enough to completely encompass the catheter in its desired final form, three dimensional forms like the corkscrew form discussed above could not be protected and would tend to fall from their own weight when they were accidentally stored or purposely sterilized at a temperature approaching the free form temperature of the material of which they were made. Similar loss of shape tended to occur when the action of the sterilizing gas on them caused them to tend to lose their preformed stiffness.